System and method for limiting incoming spam calls

ABSTRACT

A system and method for maintaining a grey list for controlling incoming calls from numbers on a telephone network. Information associated with previous calls received by the telephone is stored in the form of a grey list. The stored information includes an indication of whether each of the previously received calls passed a previous challenge. Based on the stored information, when an incoming call is received, a determination is made whether the incoming call corresponds to a call that passed a previous challenge. The incoming call connected to the telephone if the stored information indicates that the incoming call previously passed a challenge. An action is taken if the stored information does not indicate that the incoming call previously passed the challenge. The action may include blocking the call, allowing the call or providing a current challenge to the call.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.16/691,597 filed Nov. 21, 2019, which is a continuation of U.S. patentapplication Ser. No. 16/206,993 filed Nov. 30, 2018 (now U.S. Pat. No.10,523,815), which claims the benefit of priority from Canada PatentApplication No. 3020143 filed Oct. 9, 2018, the contents of whichapplications are incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The disclosed systems and methods relate to controlling incoming callsreceived from a telephone network.

BACKGROUND OF THE INVENTION

Unsolicited or other spam calls to telephones can be annoying to asubscriber who receives the calls. Unsolicited calls may be made fromparties, organizations or campaigns with which the subscriber has noprior relationship. These calls can be made by robocallers even if suchcalls are prohibited by local telecommunication rules. In some cases,unwelcomed calls may be made to attempt to sell a product or otherwisesolicit money from a subscriber. In more nefarious cases, an illegalattempt may be made to defraud the subscriber of money or property.

There are a few different general types of spam calls. Robocalls aremachine generated calls that play announcements and may connect to liveagents if the subscriber presses a digit. Push dialers are telemarketingcampaigns that utilize predictive dialers. Live agents exist in somecircumstances but are almost never used in large scale.

Robocalls are machine generated calls that typically just play amessage. Sometimes there is an option provided to connect to a liveagent. Robocalls often call from numbers with spoofed calling lineidentification (CLID) from an unreputable carrier or a hacked operatorservices trunk. Often random numbers are used within the North AmericanNumbering Plan (NANP). Sometimes a fake national or international numberis used. Sometimes an invalid number may be used. A large volume ofcalls may be sent to one NPA-NXX. The CLID is typically never the sameon each call to avoid detection. These spam calls often do not leave amessage on voice mail to avoid later detection. The spam calls oftenwait for a human answer, such as detecting the spoken word “hello”followed by silence. The spam call often can also detect standardvoice-mail tones or non-silent periods that are longer than “hello”.Often robocalls have no live agent and just have a machine generatingthe call and playing the announcements. Sometimes there is an optionprovided to the subscriber recipient of the call to press a digit andspeak to a live agent. There is often limited, if any, voice recognitionmade by the robocall. The robocalls often do not use voice mail messagefingerprinting. Robocalls often use similar predictive dialingtechniques to push dialers.

Spam push dialers are similar to robocalls in a number of ways. However,rather than being nearly entirely machine generated calls that typicallyleave a message, push dialers have machine generated calls that onlyconnect to available agents once a human answer is detected. No liveagent is connected until after a human answer is detected. Unlike mostrobocalls, push dialers may use voice mail message fingerprinting.

Current attempts to deal with spam blocking include do not call lists.However, nationally maintained telemarketing do not call lists onlyavoid cold calls from telemarketers that play by the rules. CLIDblocking may be used, but only works on spam calls that block CLD.Caller reveal may also be employed, but only works on spam calls thatblock CLD or provide invalid CLID. Some telephone users may activate aDo Not Disturb (DND) mode, but it generally would only suppress callsduring given periods or when requiring access codes. Using a DND systemmay be difficult to manage due to its complexity.

Other attempts to deal with spam calls include attempting to controlincoming calls received on a network by requiring a challenge for thespam caller, but these systems have drawbacks. In some previousattempts, a challenge is sent to an incoming call, but no informationobtained from the challenge is stored in the system. In such a system,the challenge process will need to be repeated each time a new call isreceived, which can be irritating for legitimate callers who will besubjected to repeated challenges each time they attempt to call.

SUMMARY OF THE INVENTION

There is provided in one embodiment a method of controlling callsreceived by a telephone connected to a telephone network. Informationassociated with previous calls received by the telephone is stored andthe stored information includes an indication of whether each of thepreviously received calls passed a previous challenge. Based on thestored information, when an incoming call is received, a determinationis made whether the incoming call corresponds to one of the previouslyreceived calls that passed a previous challenge. The incoming call isallowed to connect to the telephone if the stored information indicatesthat the incoming call corresponds to a previously received call thatpassed a previous challenge. An action is taken if the storedinformation does not indicate that the incoming call corresponds to apreviously received call that passed the previous challenge.

In a further embodiment, there is provided a system for controllingcalls to a telephone on a telephone network. There is a network exchangeconfigured to receive an incoming call from the telephone network. Thereis a call control processor configured to receive information relatingto the incoming call from the network exchange. The processor is furtherconfigured to compare information relating to the incoming call withstored information on a server. The stored information includes anindication of whether each of the previously received calls passed aprevious challenge. The processor is further configured to instruct thenetwork exchange to connect the incoming call to the telephone when thestored information indicates that the incoming call corresponds to apreviously received call that passed a previous challenge.

In yet a further embodiment there is a call control unit for controllingcalls received on a telephone network. A processor is configured toreceive information relating to an incoming call received by thetelephone network. The incoming call requests a connection be made to atelephone on the telephone network. A server is configured to storeinformation associated with previous calls received by the telephone.The stored information includes an indication of whether each of thepreviously received calls passed a previous challenge. The processor isconfigured to retrieve and update information on the server. Theprocessor is configured to instruct the network exchange to connect theincoming call to the telephone when the stored information indicatesthat the incoming call corresponds to a previously received call thatpassed a previous challenge.

These and other aspects of the system and method are set out in theclaims, which are incorporated here by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described with reference to the figures, inwhich like reference characters denote like elements, by way of example,and in which:

FIG. 1 is a flow diagram showing a method of controlling calls receivedby a telephone on a telephone network;

FIG. 2 is a schematic diagram of a system for controlling calls receivedfrom a telephone network;

FIG. 3 is a schematic diagram of a call control system; and

FIG. 4 is a flow diagram showing a method for controlling calls receivedby a telephone on a telephone network.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In an embodiment shown in FIG. 1 there is a method 10 of controllingcalls received by a telephone connected to a telephone network.

At 12, information associated with previous calls received by thetelephone is stored, the stored information includes an indication ofwhether each of the previously received calls passed a previouschallenge. This stored information may be described as a grey list. At14, based on the stored information, when an incoming call is received,a determination is made whether the incoming call corresponds to one ofthe previously received calls that passed a previous challenge. At 16,the incoming call to is allowed connect to the telephone if the storedinformation indicates that the incoming call corresponds to a previouslyreceived call that passed a previous challenge. At 18, an action istaken if the stored information does not indicate that the incoming callcorresponds to a previously received call that passed the previouschallenge.

Taking an action in step 18 may further include one of the following:blocking the incoming call, allowing the incoming call to connect to thetelephone or sending a current challenge to the incoming call. Thedetermination of which action to take can be set by a subscriber orbased on a set of rules set by the system or a combination of bothsubscriber choice and system evaluation steps.

A user may determine which action to take when the stored informationdoes not indicate that the incoming call corresponds to a previouslyreceived call that passed the previous challenge. The user can make thisdetermination by various means, including, for example, selecting asetting through their phone or through a web access to the servercontaining the user's settings. In some cases, the user may not want toreceive any calls from numbers that are not on the grey list. In othercases, the user may wish all calls to be routed through to the user'stelephone despite the number not being on the grey list.

In other embodiments, the method may include an evaluation step todetermine which action to take based on information about the incomingcall. For example, the determination may be made based in part onwhether the incoming call is associated with one or more of thefollowing calling line IDs: private, toll free, international, invalidand unknown. For example, as discussed in more detail below, the methodmay reject incoming calls from, for example, unknown or toll freenumbers. The method may also reject all incoming calls with thosecalling lines IDs. In some cases, as discussed in more detail below,taking the action may mean sending a current challenge to a callingtelephone that initiated the incoming call. The method may allow theincoming call to connect to the telephone if the incoming call passesthe current challenge. Once the incoming call passes the challenge, thenumber associated with the incoming call may be added to the grey listby updating the stored information to include an indication that theincoming call passed the current challenge. The current challenge mayinclude a voice prompt that requires a user response. Various challengescan be use to determine that the caller is a human and not an automatedsystem such as a robocall or push dialer. For example, the voice promptmay include a request for the caller to press a key and the userresponse may be to press the requested key. Other voice prompts andrequests could be used, including requesting that the caller say aparticular word or phrase or press a sequence of keys. The user responseshould be simple for a human to execute but should be beyond theprogramming of most incoming robocalls. To further make it difficult forthe robocall to connect to the receiving telephone, the currentchallenge may also include playing a voicemail tone after the voiceprompt. It is common for robocalls to disconnect once they detect avoicemail tone, and so the robocall may disconnect once the voicemailtone is heard. However, a human caller would be expected to realize thatthe user response can be made after hearing the voice prompt followed bythe voicemail tone.

If an incorrect first response is received in response to the currentchallenge, a second challenge of a voice prompt may be sent to the user.The second challenge may be the same prompt repeated or a new modifiedchallenge for the user. If in response to the second challenge a secondincorrect response is received, the incoming call may be blocked.Depending on the preferences of the user or optimisation of the system,the incoming call may instead by sent only one challenge, or may receivemultiple chances to pass the challenge.

As discussed in more detail below, depending on whether the incomingcall is associated with a number on a blocked caller list or allowedlist for the telephone, different actions may be taken. For example, theincoming call may be blocked when the phone number associated with theincoming call corresponds to a number on a blocked caller list for thetelephone. The incoming call may be allowed to connect to the telephonewhen a phone number associated with the incoming call corresponds to anumber on an allowed list for the telephone.

The method may also prompt the user of the telephone to add a number toan allowed list for the telephone based on its presence on the greylist. For example, if the telephone has received a number of calls froma number on the grey list, it may suggest to the user that the number beadded to the allowed list.

A schematic showing the components in a system 100 for controlling callson a telephone network 104 is shown in FIG. 2. A network exchange 106 isconfigured to receive an incoming call from a calling party 102 on thetelephone network 104. A call control processor 108 is configured toreceive information relating to the incoming call from the networkexchange 106. The processor 108 is further configured to compareinformation relating to the incoming call with stored information on aserver. The stored information includes an indication of whether each ofthe previously received calls passed a previous challenge. The processor108 is further configured to instruct the network exchange to connectthe incoming call to the telephone when the stored information indicatesthat the incoming call corresponds to a previously received call thatpassed a previous challenge. The call control processor 108 can beconfigured to send a current challenge to the calling telephone 102 thatinitiated the incoming call. The call control processor 108 may befurther configured to connect the incoming call to the telephone if theincoming call passes the current challenge. The call control processor108 may be further configured to update stored information on the serverto include an indication that the incoming call passed the challenge.

The telephone network 104 may be a Public Switched Telephone Network(PSTN) 104 switch, and the calling telephone 102 may be connected to thePSTN. Although the system is shown as a PSTN, the systems and methodsdisclosed may be used in analogous applications on other networks, suchas those that include VoIP networks or other networks that may becompatible with or alternatives to standard PSTNs. Although the callingtelephone may be described herein as a specific telephone associatedwith a specific user, the telephone may be operated by a computer andnot be associated with a physical conventional telephone. References tothe ‘user’ or ‘calling party’ or the ‘calling telephone’ are made forthe convenience of the reader and the references are also intended toinclude calls that may by robocalls, push dialing or other automaticsystems that do not use conventional systems or equipment and may nothave a human calling party.

The incoming call encounters the call control system provisioned for acalled subscriber or called party 112. Once the call is received by thenetwork exchange 106 such as for example, on a class-5 telephone switchin the PSTN, the call is directed to a processor and server such as aconverged voice application server (CvAS) 108. The CvAS may contain callcontrol service logic.

After information about the incoming call has been reviewed by the CvAS108, if the originating call subscriber is on a blocked caller list, thecall party either hears an announcement played or is directed to thevoicemail of the called party 112. In this case, the call does notcomplete. If the calling party is on an allowed list, then the callproceeds successfully to the called party 112 through the networkexchange 106.

If the calling party is on the grey list and has previously passed achallenge, then the call proceeds successfully to the called party 112through the network exchange 106.

If the calling party is not any of the lists, then the CvAS 108 may playa current challenge. The CvAS 108 may obtain media from a media server110. The media may be, for example, a recorded message that states “Thisnumber has call control. To get through, please press X”. The mediaserver 110 may store a voice prompt and the call control processor 108is configured to retrieve the voice prompt from the media server 110,and sending a current challenge to the calling telephone may includesending the voice prompt to the calling telephone. Any variation ofchallenge may be used so long as the message can elicit a specific anddetectable response from the originator of the call. If the callingparty passes the challenge, then the call is successfully connected tothe called party 112. If the calling party fails the challenge, then thecall is not connected. The calling party may hear an announcement playedthat the call has not been connected, or the call is being directed tovoicemail, or both.

As shown in FIG. 3, an embodiment of a call control unit 200 forcontrolling calls received on a telephone network 206 is described inmore detail. A processor 204 is configured to receive informationrelating to an incoming call received by the telephone network 206. Theincoming call may request a connection be made to a called telephone 208on the telephone network 206.

A server 202 is configured to store information associated with previouscalls received by the telephone. The stored information may include anindication of whether each of the previously received calls passed aprevious challenge. The processor 204 is configured to retrieve andupdate information on the server 202 and the processor 204 is configuredto instruct the network exchange to connect the incoming call to thetelephone 208 when the stored information indicates that the incomingcall corresponds to a previously received call that passed a previouschallenge. The processor 204 may be further configured to send a currentchallenge to a calling telephone that initiated the incoming call. Theprocessor 204 may be further configured to connect the incoming call tothe telephone 208 if the incoming call passes the current challenge. Theprocessor 204 may be further configured to update stored information onthe server to include an indication that the incoming call passed thechallenge.

One embodiment of a method 300 of controlling calls is shown in moredetail in FIG. 4. When a query is sent by a telephone network switchsuch as a PSTN switch to a processor such as the Converged applicationServer (CvAS) and the called party is a call control subscriber, thenthe CvAS will invoke a call control service logic 302. First, at 304 thecalling line ID (CLID) may be examined. If the CLID is unknown (blank)as shown at 356, the service 302 checks the challenge flags as describedin “C” below. If the CLID is not blank as shown at 306, the service 302checks if the calling number is on the emergency list at 308 and if sothe call will be completed. Next the service 302 checks if the callingnumber is on the subscriber's allowed callers list at 310 and if so thecall will be completed. The service then checks if the calling number ison the subscriber's blocked callers list at 312 and if so the call willbe blocked as per “B” below. If the calling number is on a Global acceptor block lists at 314 then the call goes to “C” to check the challengeflags as shown at 324.

If the caller was not on any of the above lists, the grey list ischecked as shown at 316. The grey list is a list of, for example, the 25most frequent callers who have previously passed the challenge. In otherembodiments, the grey list can include any number of callers who havepreviously passed a challenge. If the caller is on the grey list, acounter associated with that caller is incremented as shown at 320 andthe call goes to “C” to check the challenge flags at 324. If the calleris not on the grey list, the caller is considered a first time caller asshown at 318 and is temporarily added to the grey list as shown at 322and then the call goes to “C” to check the challenge flags.

At 324, the challenge flags are checked, which is step “C”. Thesubscriber can chose to allow at 328, block at 330 or challenge at 332callers based on whether the caller is a first time caller, or on thegrey list. Other criteria can also be used such as whether the callingnumber is:

a. Private

b. Toll Free

c. International

d. Invalid

e. Unknown

f. Other

If the chosen action is to allow the call at 328, then the call iscompleted as per “A” at 342. If the chosen action is to block the callat 330, then the caller is blocked as per “B” at 352.

If the chosen action is to challenge the call at 332, then the challengeannouncement is played at 334 to the caller using a Media Server. Anexample challenge could be the following: “This number has Call Control.To get through, please press x”, where x is a random digit between 1 and10. At the end of the challenge announcement a voice mail tone isplayed. If the caller is a robocaller, the robocaller will assume theyhave reached the subscribers voice mail and will not complete the call,which will result in the caller failing the challenge at 346. The callermay be given two tries to enter the correct digit. If they fail to enterthe correct digit at 346 and fail again after a second attempt at 348,the caller's number is removed from the grey list at 350 and the call istreated as per “B” at 352. If the caller enters the correct digit at338, the call is treated as per “A” at 342 after the challenge flag isset on the grey list at 340.

At step 352, which is step “B”, the call information is recorded in thesubscriber's call log at 352 and the caller is played a terminatingannouncement using the Media Server or sent to the subscriber's voicemail at 354. The decision about which response to provide to a numberthat is not added to the grey list may be set by the subscriber,depending on the subscriber's previous choice.

At step 342, which is step “A”, the call information is recorded in thesubscriber's call log and the caller is connected to the subscriber at344.

In some embodiments, the grey listing service may use CvAS service logicthat hangs off of termination-attempt trigger, which is the same as DNDmode. It can be invoked prior to DND. The list may maintain a list ofthe most-recent, most-frequent number of callers indexed by valid CLID.For example, 25 caller may be indexed at a time. Callers with invalid orblocked CLID may be treated as first-time callers and not placed onlist. Numbers on the grey list with presentable CLID may be displayed toa customer in DND web interface as suggested numbers for a call allowedlist or white list. A DND web interface can permit subscribers to deletecallers from the grey list (resetting them to first-time callers). Thegrey list can be maintained regardless of whether “Call Guard” or DND isactivated. The grey list can operate with regular DND service offering.When DND service is active, the call may be passed to regular DNDservice logic. When DND service is inactive and optional “Call Guard”service is inactive it connects the call as normal. When DND service isinactive and optional “Call Guard” service is active, the call ishandled by Call Guard service logic.

When invoked, Call Guard service logic may challenge first-time callerswith an announcement (prompt and collect) requesting the caller to inputa digit. Announcement can be something like: “The number you have calledis not accepting unsolicited calls at this time. Please enter <randomdigit> after the tone to proceed. <voice mail tone>”. <random digit> isa randomly selected number from 0 to 9. <voice mail tone> is thestandard voice mail tone or “beep”. First-time callers may be definedas:

-   -   a. A caller with an invalid CLID.    -   b. A caller with a blocked CLD.    -   c. A caller with a valid CLID that is not on the DND white list.    -   d. A caller with a valid CLID that was entered on the grey        without challenge less than 24 hours ago.

In some cases, subscribers may block invalid CLIDs or Private CLIDs ifthey choose, and so the service may not automatically treat them asfirst-time callers. First-time callers with a valid CLID that pass thechallenge are added to the grey list. First-time callers that fail thechallenge are removed from the grey list. Because there is no live agentto understand the message, unsolicited, CLID-spoofed robocalls should beeffectively suppressed. Because there is no live agent until a humananswers, CLID-spoofed predictive dialed spam calls should be effectivelysuppressed. Live agent spam calls will not be suppressed, but the systemmay collect the necessary information for user reporting. Falsepositives can be corrected by a subscriber adding the number to a DNDwhite list or allowed list. In some embodiments, the system may trackand report the number of failed challenges and suppressed calls. Userreporting tools may allow service providers to refine the suppressionlogic by pulling up call traces for calls that failed suppression.

Because service can be implemented in Converged Application Server(CvAS) service logic, all copper subscribers may be covered. Fortelecommunications companies, implementation on CvAS requires no capitalequipment beyond basic DND service. Extension to IP Multimedia Subsystem(IMS) core, such as Voice over Long-Term Evolution (VoLTE) and NextGeneration Home Phone (NGHP), is possible using Application Server (AS)from Dialogic.

In order to implement the system and method disclosed, the system mayuse proof of concept (PoC) with Dialogic to extend termination-attempttrigger from IMS to CvAS. Advanced Intelligent Network (AIN) triggersmay be extended from IMS core into CvAS to provide residential AINservices to Home Phone to Go (HP2G). AIN triggers may be extended fromIMS core into CvAS to provide business AIN services to IMS-basedbusiness services (when Business Voice over Internet Protocal (BVoIP)goes to IMS).

Immaterial modifications may be made to the embodiments described herewithout departing from what is covered by the claims. For example, eachof the processor or server or other systems disclosed may be physical,virtual or cloud-based systems so long as each is capable ofimplementing the method disclosed. In those cases where the systems arephysical, the functionality described for each of the processor orserver or other systems may be implemented by a single piece of hardwareat a specific location or may make use of multiple systems at separatelocations. The processor and server themselves may be provided togetheron a single piece of hardware or multiple pieces of hardware. Thenetwork systems described may be entirely digital or analog or a mixtureof the two so long as the necessary connections may be made betweentelephone users.

In the claims, the word “comprising” is used in its inclusive sense anddoes not exclude other elements being present. The indefinite articles“a” and “an” before a claim feature do not exclude more than one of thefeature being present. Each one of the individual features describedhere may be used in one or more embodiments and is not, by virtue onlyof being described here, to be construed as essential to all embodimentsas defined by the claims.

While the preferred embodiment of the invention has been illustrated anddescribed, as noted above, many changes can be made without departingfrom the spirit and scope of the invention. Accordingly, the scope ofthe invention is not limited by the disclosure of the preferredembodiment. Instead, the invention should be determined entirely byreference to the claims that follow.

1.-24. (canceled)
 25. A method of controlling calls received by a telephone connected to a telephone network, comprising: determining whether to send a current incoming call from a phone number a current challenge prior to connecting the current incoming call to the telephone based on information related to the phone number including one or more of the following: a) a property of a calling number identification associated with the phone number; b) the presence of the phone number on a white list, a grey list or a blocked caller list; c) stored information indicating whether a previous incoming call from the phone number to the telephone passed a previous challenge; or d) stored information including the frequency and the recentness of previous calls from the phone number; sending a current challenge to the phone number, the current challenge comprising a request for a user associated with the current incoming call to press a randomly-selected digit or digits and in which the current challenge is passed if the requested randomly-selected digit or digits is pressed; and allowing the current incoming call to connect to the telephone if the current challenge is passed.
 26. The method of claim 25 in which the information related to the phone number further comprises an indication of whether the previous incoming call from the phone number to the telephone passed the previous challenge; and the method further comprising allowing the current incoming call to connect to the telephone if the current incoming call corresponds to a previously received call that passed a previous challenge.
 27. The method of claim 26 in which a user associated with the telephone determines whether to block, allow or send the current challenge to the current incoming call when the information related to the number associated with the current incoming call does not indicate that the current incoming call corresponds to a previously received call that passed the previous challenge.
 28. The method of claim 25 in which the current challenge further comprises playing a voicemail tone after a voice prompt, wherein the voice prompt comprises the request for the caller to press a randomly-selected digit or digits.
 29. The method of claim 25 in which the current challenge includes a first challenge and a second challenge, and in which the current incoming call is sent a second challenge if a first incorrect response is received in response to the first challenge.
 30. The method of claim 29 further comprising blocking the current incoming call if in response to the second challenge a second incorrect response is received.
 31. The method of claim 25 further comprising providing a prompt to a user associated with the telephone to add the phone number to an allowed list for the telephone if the phone number associated with the previous incoming call or the current incoming call passed the previous challenge or the current challenge.
 32. The method of claim 25 in which the current incoming call from the phone number is blocked if the calling number identification associated with the phone number is not valid.
 33. The method of claim 25 further comprising a storing a grey list and in which first-time callers to the telephone are sent the current challenge and if the phone number associated with the first-time caller passes the current challenge, then the first-time caller is added to the grey list.
 34. The method of claim 25 further comprising providing a user associated with the telephone an option to direct incoming calls to voicemail if the phone number fails the current challenge.
 35. A system for controlling calls to a telephone on a telephone network, comprising: a network exchange configured to receive a current incoming call from the telephone network; and a call control processor configured to receive information relating to the current incoming call from the network exchange, the processor further configured to: determine whether to send the current incoming call from a phone number a current challenge prior to connecting the current incoming call to the telephone based on information related to the phone number including one or more of the following: a) a property of a calling number identification associated with the phone number; b) the presence of the phone number on a white list, a grey list or a black list; c) stored information indicating whether a previous incoming call from the phone number to the telephone passed a previous challenge; or d) stored information including the frequency and the recentness of previous calls from the phone number; send a current challenge to the phone number, the current challenge comprising a request for a user associated with the current incoming call to press a randomly-selected digit or digits and in which the current challenge is passed if the requested randomly-selected digit or digits is pressed; and allow the current incoming call to connect to the telephone if the current challenge is passed.
 36. The system of claim 35 in which the call control processor is further configured to store a grey list and in which first-time callers to the telephone are sent the current challenge and if the phone number associated with the first-time caller passes the current challenge, then the first-time caller is added to the grey list.
 37. The system of claim 35 further comprising a media server connected to the call control processor, the media server storing a voice prompt and the call control processor being further configured to retrieve the voice prompt from the media server, and in which sending a current challenge to the telephone further comprises sending the voice prompt to the telephone.
 38. The system of claim 37 in which the call control processor is further configured to play the voice prompt followed by a voicemail tone to the user associated with the phone number, wherein the voice prompt comprises the request for the user associated with the phone number to press a randomly-selected digit or digits.
 39. A call control unit for controlling calls received on a telephone network, comprising: a processor configured to receive information relating to a current incoming call associated with a phone number received by the telephone network, the current incoming call requesting a connection be made to a telephone on the telephone network; a server configured to store information related to the phone number including one or more of the following: a) a property of a calling number identification associated with the phone number; b) the presence of the phone number on a white list, a grey list or a black list; c) stored information indicating whether a previous incoming call from the phone number to the telephone passed a previous challenge; or d) stored information including the frequency and the recentness with previous calls from the phone number; and the processor being configured to: determine whether to send a current incoming call from a phone number a current challenge prior to connecting the current incoming call to the telephone based on the information stored on the server related to the phone number; send a current challenge to the phone number, the current challenge comprising a request for a user associated with the phone number to press a randomly-selected digit or digits and in which the current challenge is passed if the requested randomly-selected digit or digits is pressed; and allow the current incoming call to connect to the telephone if the current challenge is passed.
 40. The call control unit of claim 39 in which the processor is further configured to store a grey list and in which first-time callers to the telephone are sent the current challenge and if the phone number associated with the first-time caller passes the current challenge, then the first-time caller is added to the grey list.
 41. The call control unit of claim 39 further comprising a media server connected to the processor, the media server storing a voice prompt and the processor being further configured to retrieve the voice prompt from the media server, and in which sending the current challenge to the telephone further comprises sending the voice prompt to the telephone.
 42. The call control unit of claim 41 in which the call control processor is further configured to play the voice prompt followed by a voicemail tone to a user associated with the phone number, wherein the voice prompt comprises the request for the caller to press a randomly-selected digit or digits. 